Photoinduced electron-transfer processes involving covalently linked ruthenium and cobalt polypyridyl complexes. Comparison of electronic coupling in bridged and nonbridged ruthenium and cobalt complexes

Journal Article · Thu Apr 01 00:00:00 EST 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100115a026· OSTI ID:6259133

Song, Xiaoqing; Lei, Yabin; Endicott, J F ^[1]; Van Wallendal, S; Jackman, D C; Rillema, D P ^[2]; Perkovic, M W ^[3]

---

1. Wayne State Univ., Detroit, MI (United States)
2. Univ. of North Carolina, Charlotte (United States)
3. Wayne State Univ., Detroit, MI (United States) Univ. of North Carolina, Charlotte (United States)

Photoinduced electron-transfer processes have been examined in a heterobimetallic coordination complex with polypyridyl ligands. Three relaxation processes were observed to follow light absorption by (bpy)[sub 2]Ru(bb)Co(bpy)[sub 2][sup 5+] (where bpy = 2,2'-bipyridine and bb 1,2-bis(2,2'-bipyridyl-4'-yl)ethane) with lifetimes in water at 25[degrees]C of 0.18, 1, and 6 ns determined using picosecond flash photolysis techniques. These nearly solvent independent relaxation rates are ascribed to forward electron transfer from ([sup 3]MLCT)Ru(bpy)[sub 2][sup 2+] to Co(bpy)[sub 2][sup 3+], spin relaxation at the Co(II) center and back electron transfer from ([sup 4]T[sub 1])Co(bpy)[sub 2][sub 2+] to Ru(bpy)[sub 2][sup 3+]. Luminescence decay of ([sup 3]MLCT)Ru(bpy)[sub 2][sup 2+] has also been used to monitor the electron-transfer quenching step from 77-150 K, and the quenching rate extrapolated to 25[degrees]C (activation energy of 2.2 [times] 10[sup 3] cm[sup [minus]1]) was compatible with the 180-ps lifetime. It is inferred that the back electron transfer rate is retarded by poor donor-acceptor electronic coupling (k[sub el] [congruent] 10[sup [minus]3]). A Mulliken type of perturbational model is proposed to describe the weak electronic coupling in this complex. Spectroscopic parameters are combined with the perturbational expressions to give a plausible account of the electronic coupling in the back-electron-transfer process. 84 refs., 9 figs., 5 tabs.

• DOE Contract Number: FG05-84ER13263; FG02-88ER13944
• OSTI ID: 6259133
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 97:13; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
COBALT COMPLEXES
ELECTRON TRANSFER
PHOTOLYSIS
RUTHENIUM COMPLEXES
BIPYRIDINES
MATHEMATICAL MODELS
PERTURBATION THEORY
RELAXATION
THEORETICAL DATA
AZINES
CHEMICAL REACTIONS
COMPLEXES
DATA
DECOMPOSITION
HETEROCYCLIC COMPOUNDS
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PYRIDINES
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
360602 - Other Materials- Structure & Phase Studies